.nav {
  height: 100px;

  ul {
    margin: 0;

    li {
      float: left;
      list-style: none;
      padding: 5px;
    }

    a {
      display: block;
      color: green;
      padding: 5px;

      &:hover {
        background-color: blue;
        color: yellow;
      }
    }
  }

  & &-text {
    font-size: 15px;
  }

  border: 1px solid red {
    left: 0;
    right: 0;
  }
}

// 属性嵌套
body {
  font: {
    family: "Microsoft YaHei UI";
    size: 15px;
    weight: bold;
  }
}

